BISMARCK, N.D. (KFYR) – Water and food coloring are all that you need to do some easy science experiments at home that explain how our atmosphere works with fronts, convection, and thunderstorms! This is all possible because the atmosphere is a fluid — it’s a mixture of gasses that behaves like a liquid. Like water, the pressure at the bottom of the atmosphere, near the ground, is higher than the pressure near the top of the atmosphere. Fluids move in response to differences in pressure, always flowing from high toward low pressure. The is the same with liquid as it is with the air in our atmosphere. Therefore, we can use water to represent our atmosphere and the different temperatures of that water to create movement and circulations.
Our first experiment will represent what weather fronts look like in 3-D and how air density plays a role in our atmosphere.
You’ll need a clear baking tray that’s fairly deep (or a clear storage container), a glass of ice-cold water with blue food coloring, and a glass of hot water with red food coloring. Fill the clear tray with lukewarm water — something in between the temperature of your ice cold water and hot water.
Get ready to pour the cold water into one side of the tray and the hot water into the other side of the tray simultaneously. Pour them in slowly and watch what happens when the two colors meet in the middle.
As the different temperatures of water, and their respective colors, meet in the middle of the tray you’ll notice the cold water goes underneath the warm water. This sloped surface with the cold, dense water at the bottom and the hot, less dense water riding up and over the colder water illustrates a weather front well.
As shown in the 3-D cold front diagram below, a front is a sloped surface with the advancing dense, cold air undercutting the less dense warm air, which gets pushed up higher into the atmosphere. This upward, rising motion of the warm air is what forms clouds, precipitation, and thunderstorms along these fronts.
A warm front is similar, but in its case, the warm air is advancing and it glides over the cooler and more dense air. Usually, with warm fronts, the precipitation is more steady and widespread compared to cold fronts, although thunderstorms can also occur with warm fronts.
The main concept that we learned from this simple science experiment is that cold air is denser than hot air (the same applies to our cold water and hot water) and weather fronts are sloped surfaces with the cold air undercutting the warm air. This is why you see active weather, and sometimes severe weather, where areas of hot and cold air meet, usually along these fronts.
Our second simple science experiment will demonstrate convection in our atmosphere, which is the process that forms thunderstorms.
You’ll need the same clear baking tray that’s fairly deep (or a clear storage container), fill it with cool water (but not too cold), and put it on top of a few empty glasses — one at each corner. Then, fill up another glass all the way to the top with hot water and put some red food coloring in it. Slide this glass underneath the tray into the center.
Place a few drops of blue food coloring on either side of the tray of cool water and a few drops of red food coloring in the center of the tray, right over the glass of hot water that’s underneath the tray. The drops of food coloring will begin to sink to the bottom and disperse. You’ll have to be a bit patient with this experiment, but watch closely what happens. As the hot water in the glass under the center of the tray heats up the water in the center of the tray, the water and red food coloring start to rise to the surface as the water becomes warmer and less dense than its surroundings. To replace the water that’s rising, the cooler water and blue food coloring sink to the bottom of the tray and move to the center. When this cooler water is drawn into the center of the tray, it gets heated up by the glass of hot water underneath, rises to the top, and the process continues. This is a convection current, and it’s similar to the process that happens in our atmosphere.
Below is a close-up of the food coloring rising up from the bottom of the tray to the top of the tray over the heat source, which is the glass of hot water. Then, the water and food coloring spread out at the top of the tray, which simulates the top of our atmosphere. Rising air forms clouds and thunderstorms, but these clouds can only grow to a certain height before the top of our atmosphere spreads out the tops of the clouds.
The convection current in our experiment will continue for a while, but the colors of food coloring will start to mix over time. Be sure to observe all the cool things that the different colors and temperatures of water do in the tray!
Convection, which we demonstrated in this second experiment, is an important part of our atmospheric processes that form clouds and precipitation. It’s a process that first starts with the radiation from the sun, which heats the ground. But the ground is heated unevenly across the globe, so some areas end up warmer than others. The warm ground then heats the air around it through the conduction process. Then this warmer, less dense air rises in the convection process. As the warm air rises, it encounters cooler layers of the atmosphere which allow the water vapor molecules to condense into clouds. And when the water droplets in clouds combine, they become heavy enough to form raindrops. If the rising air, or updrafts, are strong enough, thunderstorms can form.
The convection current that we demonstrated in our experiment translates to our atmosphere with warm air rising to form clouds, spreading out when it reaches the top of the atmosphere, then cooler air sinking around it. Cooler air near the ground gets heated up and it starts to rise as well, increasing the size of the cloud as more warm, moist air rises. This forms an essentially endless loop as long as the sun provides a heating source to warm up the ground (which is similar to our glass of hot water under the tray as the heat source in our experiment).
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